Tamriel Rebuilt (also known by the abbreviation 'TR3' on UESP) is the largest collaborative fan-based modding project for the Elder Scrolls series. This project has existed since before Morrowind's release, though the leadership and members have changed many times since then. They are currently creating the mainland of Morrowind on Morrowind's engine.

Tamriel Rebuilt is a group collaboration, a project which has involved over 200 modders and contributors over the years. Tamriel Rebuilt was founded in 2002 by a gaming enthusiast under the alias 'Ender', before Morrowind was even released. Sacred East, as well as updates, bug fixes and new quests for Telvannis and Antediluvian Secrets, was released on 6 June 2012. The latest release, build 16.03, includes additions to the preview and travel files, a new heightmap for the southern lands, and several notable bug fixes. It was made public on March 30, 2016.

Tamriel Rebuilt progresses 'in stages', a term which essentially translates that one area of modding must be completed before work can begin on another. The order of progression typically starts off with heavy planning, which includes forming details for important NPCs, questlines, locations, and overall concepts. Then it leads into worldspace creation, with exteriors constructed to cater for interior design. Once the worldspace has been created, inhabitants including both NPCs and creatures are included, and then accompanying dialogue, and later quests.

Files for Tamriel Rebuilt are organized into individual 'claims'. The claims are managed in different departments, encompassing all the aspects of the mod. The departments are divided into those of Exteriors, Interiors, Quests, Objects, and Sound. Once a claim has been fulfilled by a developer, it undergoes a vigorous 'Reviewing' process. Designated users thoroughly examine every aspect and detail added by the claim, deciding if it fits the impeccable criteria required to be merged into the mod and eventually released to the public. Moderators and Administrators must then confirm the claim, although if the standard is not adequate the claim can be rejected and returned to the original developer for a re-design.

Tamriel Rebuilt's forums are also divided and the visibility and access is restricted to certain members of the project. Guests and Members can view most sub-forums, while Tamriel Rebuilt developers can view additional subforums for internal releases and design for the mod. Senior and Lead Developers can also access hidden sub-forums for further purposes, which typically deal with the formation of new plans and ideas for the mod.

Prior to 2010, Tamriel Rebuilt was billed to divide the mainland of Morrowind into six distinct maps, all of which were to be developed separately and sequentially. Due to a re-organization in 2009, the number of six was increased to eight, to increase productivity and general public accessibility. After further re-organization in 2014, the TR team had again changed the project's release structure, focusing on releasing playable areas as they're finished rather than the eight major planned "releases". The project's vision had also undergone a change, and now plans to eventually integrate itself with vanilla content.

Maps that have been released to the public include Map 1 ('Telvannis'), Map 2 ('Antediluvian Secrets'), and Map 3 ('Sacred East'). Both Telvannis and Antediluvian Secrets cover the regions ruled by the House Telvanni, while Sacred East is centered around cities of House Indoril and the city of Necrom. Upcoming releases will be focused around the Thirr River Valley region, as well as the Imperial city of Old Ebonheart. Future releases will no longer be labelled as maps.